Sheet holding mechanism

ABSTRACT

A sheet holding mechanism for receiving and stacking sheets such as recording papers ejected from a main apparatus such as, for instance, a printer. The mechanism comprises an ejected sheet tray provided to the main apparatus that is swingable in a predetermined range. The tray is lockable by lock means at every predetermined angle in the above predetermined range. Guide roller means provided to the main apparatus lead the sheet ejected from the main apparatus to the tray and is arranged to be swingable in response to swing movement of the tray.

BACKGROUND OF THE INVENTION

The present invention relates to a sheet holding mechanism of anapparatus, such as a copying machine, a printer or the like, fortransferring data onto a recording sheet.

Heretofore, copying machines, printers and the like have been known fortransferring data onto recording sheet.

Such an apparatus is arranged so that a recording sheet introduced froma recording-sheet introducing port into the apparatus is subjected to apredetermined processing, such as copying, printing and the like beforebeing ejected from a sheet eject port.

An ejection sheet tray is normally attached to one side where the sheeteject port of the apparatus is located and sheets of recording sheetejected from the sheet exhaust port are placed and stacked on the sheettray.

However, the sheet tray has to be larger in size than the maximum sizeof the recording sheet that the apparatus can deal with. Accordingly,the apparatus needs a wide space for installation only because of thesheet tray, despite the fact that the tendency is for the apparatus tobe made compact.

In view of the installation space and operability, it is needless to sayadvantageous if the angle of the sheet tray is freely adjustable.Notwithstanding, difference in angle between the sheet eject from thesheet eject port and the sheet tray may cause sheet-jamming. The problemis that the sheet cannot be ejected onto the sheet tray smoothly.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a sheet holdingmechanism capable of ejecting sheets onto an ejected sheet tray withoutcausing sheet-jamming even though the angle of the sheet tray isaltered, so that this arrangement may contribute to not only savinginstallation space but also resulting in the improved operation of theapparatus.

In order to accomplish the foregoing object according to the presentinvention, a sheet holding mechanism stacking sheets ejected from a mainapparatus, comprises an ejected sheet tray that is swingably pivoted tothe main apparatus at one end which is formed as a ratchet wheel; a pawlmember swingably pivoted to the main apparatus and biased in thedirection to mesh with the ratchet wheel of the ejected sheet tray; anda roller supporting member swingably pivoted to the main apparatus forsupporting guide rollers which lead the sheet outputted from the mainapparatus to the ejected sheet tray, the roller supporting member beingbiased to upwardly swing and being swung downwardly in response todownward swing movement of the ejected sheet tray.

DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 is a schematic side view illustrating a laser beam printer towhich a paper exhaust unit embodying the present invention is applied;

FIG. 2 is a partial enlarged elevational view of the paper exhaust unit;

FIG. 3 is a sectional view taken on line III--III of FIG. 2;

FIG. 4 is a sectional view taken on line IV--IV of FIG. 2; and

FIG. 5 is a left-hand side view of FIG. 2.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is a schematic side view illustrating a laser beam printer towhich a paper eject unit embodying the present invention is applied,this printer being a so-called page printer in which cutsheets cut intopredetermined sizes are used.

The laser beam printer 10 shown in FIG. 1 looks like a rectangularparallelepiped with its top diagonally cut at a predetermined angle.

The uppermost section of body 40 forms a cassette holding portion 12 toreceive a pair of paper cassettes 13, 13 in which papers of differentsizes to each other are stored, respectively. During the execution of aprinting operation, the recording papers are sequentially introduced oneby one into a paper feed path 30. An ejected paper tray 22 is providedto the side of the body 40 opposite in the diagonal direction to acassette holding portion 12.

A pair of opposed feed rollers 33, 33 are respectively provided to thecover plates 31, 32 one of which is driven to rotate by a drive means,not shown.

A photoconductive drum 1 is disposed under the substantially centralarea of the paper feed path 30 in the body 40.

Around the photoconductive drum 1 in the body 40, the following unitsare disposed along the direction of its rotation in the order describedbelow: a cleaning unit 2 for removing toner remaining on the surface ofthe drum 1, a charging unit 3 for uniformly charging the surface of thedrum 1, an laser scanning unit 4 for scanning the charged surface of thedrum 1 with laser beams carrying image data to form a latent imagethereon, and a developing unit 5 for putting toner onto the portion ofthe surface of the drum 1 exposed to the laser beams to develop a tonerimage. A reference numeral 8 represents a control unit for controllingthe operation of the printer 10, including a power source.

Corona charger 61 charges the recording paper 11 so that the toner imageon the drum 1 transferred thereonto is disposed opposedly to the drum 1with the paper feed path 30 therebetween. The corona charger 61 and theportion of the drum 1 opposed thereto constitute a transfer unit 6.

A fixing unit 7 is arranged downward stream of the transfer unit 7 alongthe paper feed path 30. The fixing unit 7 comprises a heat roller 71 anda backup roller 72 opposedly disposed with defining the paper feed path30 therebetween. The recording paper 11 carrying the unfixed toner imageis nipped between the rollers 71, 72 and the toner is fixed onto therecording paper 11 by heat and pressure applied by the heat roller 71. Adrive motor, not shown, is employed to rotate the heat roller 71 to feedthe recording paper 11 in the fixing unit 7.

The laser beam printer thus constructed operates as follows:

The recording papers 11 stored in any one of the paper cassettes 13fitted to the cassette holding portion 12 of the body 40 are drawn outthereof one by one into the paper feed path 30. The recording paper 11thus introduced into the paper feed path 30 is fed by the feed rollers33, 33. The toner image formed on the surface of the photoconductivedrum 1 is transferred to the undersurface of the recording paper 11 atthe transfer unit 6. The toner image transferred onto the undersurfaceof the recording paper 11 is fixed by the fixing unit 7, and therecording paper 11 is then ejected onto an ejection paper tray 22 withits image-carrying side down (i.e. in facedown state).

A paper eject unit 20 embodying the present invention is disposed aheadof the recording paper feed path (i.e. the paper exhaust path).

The paper exhaust unit 20, as shown in a partial enlarged elevationalview in FIG. 2, in a sectional view taken on line III--III of FIG. 2 inFIG. 3, and in a sectional view taken on line IV--IV of FIG. 2 in FIG. 4and in a left-hand side view of FIG. 2 in FIG. 5 comprises a pair ofeject paper driving rollers 21 and an ejected paper tray 22, the pair ofthe rollers and the tray being fitted to a frame 14 of the printer insuch a manner that they are independent of each other.

The pair of eject paper driving rollers 21 are arranged so that a rollershaft 21C with a drive roll 21B fixed at a predetermined position isrotatably fitted to a roller base 21A having both ends projectedperpendicularly to the lateral direction of the printer and that a pressroll 21D is biased by leaf springs 21E which is L-shaped in section andpress-fitted to the upper side of the drive roll 21B. Moreover, thesurface of the roller base 21A is fitted with a guide member 21F havingits upper end face as a diagonal plane extended toward the contactbetween the drive roll 21B and the press roll 21D and having a pluralityof triangular ribs 21G.

The roller base 21A has both ends coupled to brackets 15 perpendicularlyfixed to the frame 14 via pins 16 and always biased by springs 17 woundon the respective pins 16 so as to rock upwardly. Gears 25 fixed to therespective ends of the roll shaft 21C engage with gears 71G for drivingthe heat roll 71 of the fixing unit 7 to rotate via gears 26 fixed tothe pins 16. The roll shaft 21C (i.e. the drive roll 21B) is thus drivento rotate synchronously with the rotation of the heat roller 71.

The paper tray 22 is fitted to the brackets 15 perpendicularly fixed tothe frame 14 via arms 23 fixed to both sides of the paper tray 22 bymeans of respective pins 24 and capable of rocking. In other words, thepaper tray 22 is fixed to the brackets 15 (frame 14) in such a mannerthat it is capable of rocking about the pins 24.

A plurality of ratchet teeth 23A are formed around each pin 24 at thefront end of the arm 23 and a ratchet pawl 27 engages with the ratchettooth 23A, the ratchet pawl being rotatably mated with the pin 16 fittedto the roller base 21a and so biased by a spring 27A so as to be capableof rocking in the direction of the ratchet teeth 23A. The paper tray 22capable of rocking about the pins 24 is locked at a given angle at whichthe ratchet teeth 23A engage with the ratchet pawls 27. Release members27B are used to release the ratchet pawls 27 from engaging with therespective ratchet teeth 23A when the paper tray 22 is rocked upward byover a predetermined angle. A continuous line of FIG. 3 illustrates areleased state.

An operating lever 22A for driving the pair of eject paper drive rollers21 projects from the front end of the paper tray 22. When the rear endsurface of the roller base 21A of the pair of the eject paper driverollers 21 rocking upwardly abuts against the operating lever 22A, theupward rocking of the pair of the eject paper drive rollers 21 isrestricted thereby.

The rocking of the pair of eject paper drive rollers 21 is accordinglyinterlocked with that of the paper tray 22. In proportion to the setrocking angle of the paper tray 22, the pair of eject paper driverollers 21 are arranged so that their set angle allows the recordingpaper from the fixing unit 7 to be guided in between the pair of ejectpaper drive rollers 21 and the recording paper being fed by the pair ofeject paper drive rollers 21 to be guided onto the paper tray 22.

With this arrangement, the recording paper 11 subjected to fixation andfed from the fixing unit 7 has it front end abut against the ribs 21G ofthe guide member 21F of the pair of eject paper drive rollers 21. Beforebeing ejected onto the paper tray 22, the recording paper 11 is guidedin between the drive roll 21B and the press roll 21D and driven to befed as the drive roll 21B rotates. If the set angle of the paper tray 22is adjusted to downwardly rock, as shown by an imaginary line in FIGS. 3and 4, the paper eject drive roller 21 is caused to rock downward as thepaper tray 22 rocks and the recording paper can be driven to be ejectedfrom the fixing unit 7 onto the paper tray 22.

The paper eject unit according to the present invention is designed sothat the angle of the paper tray is made adjustable in that the pair ofrollers for driving the recording paper to be guided onto the papertray, whereby the recording paper can be ejected onto the paper traywithout trouble such as paper-jamming caused by altering the set anglethereof.

As a result, the angle of the paper tray becomes adjustable over a widerange with the effect of allowing such a printer to be installed in aspace so small as to be unfit for a regular printer, whereas theoperability of the printer is also improved.

What is claimed is:
 1. A sheet holding mechanism for receiving andstacking sheets ejected from a main apparatus, comprising:an ejectedsheet tray that is swingably pivoted to said main apparatus, one end ofsaid ejected sheet tray forming a ratchet wheel; a pawl member that isswingably pivoted to said main apparatus and which is biased in adirection to mesh with said ratchet wheel of said ejected sheet tray;and a roller supporting member that is swingably pivoted to said mainapparatus for supporting guide rollers which lead a sheet that isoutputted from said main apparatus to said ejected sheet tray, saidroller supporting member being biased to swing upward with an upwardpositioning of said ejected sheet tray, while being swung downward inresponse to a downward positioning of said ejected sheet tray so that anangle between a sheet feed path of said main apparatus and said ejectedsheet tray is changed based upon the swinging movement of said ejectedsheet tray so that a sheet can be guided onto said ejected sheet tray.2. The sheet holding mechanism according to claim 1, wherein saidejected sheet tray is provided with a contact member which contacts saidroller supporting member in such a fashion that said contact memberdownwardly pushes said roller supporting member against a biasing forcewhen said ejected sheet tray is downwardly swung.
 3. The sheet holdingmechanism according to claim 1, wherein said roller supporting member isprovided with a plurality of guide ribs, upper surfaces of said guideribs being extended to guide said sheet ejected from said main apparatustoward a nip between said guide rollers.